1. Field of the Invention
The present invention relates to an endoscope light source apparatus with a detachable flash unit
2. Description of the Related Art
In recent years, endoscopes have been widely used not only in the medical field but also in industrial fields.
In order to take pictures of an image observed by the endoscope and sent through an image guide of the endoscope, the light source apparatus of the endoscope generally includes an exposure adjustment means for adjusting an exposure and a control means for controlling the exposure adjustment means. The light source apparatus of this type has a special sequence of photographic operations.
FIG. 1 shows a conventional example of a general photographic system 1 of images observed by the endoscope.
A still camera 3 is mounted on an eyepiece unit of an endoscope (hereinafter referred to as "a scope") 2. The light of a light source apparatus 5 can be supplied to an end surface of a light guide 6 by connecting the end of a light guide cable 4 extending from an operation unit of the scope 2 to a light source apparatus 5.
That is, the light of a lamp 8 which serves as a light source and which flashes by power supplied from a lighting means 7 is condensed by a lens 9, and the amount of condensed light is then adjusted by a stop 11 before it reaches the incident end surface of the light guide 6.
A shutter 12 is detachably provided in an optical path between the stop 11 and the end surface of the light guide 6. Mounting and removal of the shutter 12, together with the aperture of the stop 11, are controlled by a photographic control means 13.
The photographic control means 13 also controls the lighting means 7.
The system 1 can be operated in either the automatic exposure control mode or the manual exposure control mode. In the automatic exposure control mode, when the release operation is performed, the shutter 12 is closed first, as shown in FIG. 2 b, and thereby blocks the light from being sent to the scope 2. At the same time, a shutter of the camera 3 is opened, as shown in FIG. 2 c. Thereafter, the shutter 12 is opened and, at the same time, the amount of light emitted from the lamp 8 is increased by the photographic control means 13 through the lighting means 7, as shown in FIG. 2a, and semi-flashing of the lamp 8 is thereby attained. While the lamp 8 is maintained in the semi-flash state, the photographic control means 13 determines whether or not correct exposure is reached on the basis of the signal sent from a photometric means (not shown) of the camera 3. Once the correct exposure is reached, the photographic control means 13 closes the shutter 12 and at the same time, through the lighting means 7, suspends semi-flashing of the lamp 8, drops the flashing level temporarily to prevent rear marks and then brings it back to a normal flashing level.
Subsequently, the shutter in the camera 3 is closed and the shutter 12 is opened.
Series of these operations are controlled by the photographic control means 13.
In the manual exposure control mode, the same operations are performed as those in the automatic exposure control mode with the exception that the shutter closes when a preset exposure time is reached even if correct exposure level is not attained.
FIG. 3 shows a photographic system 16 including a light source apparatus 15 with a large capacity flash control means 14.
The photographic system 16 differs from the system 1 shown in FIG. 1 in that, as shown in FIG. 4, the lamp 8 does not semi-flash but flashes at a large intensity by the control of the flash control means 14 when the release operation is performed. In consequence, the time required to attain the correct exposure level is reduced and a less blurred image can thereby be obtained. A cooling fan 17 is provided to prevent burning of the light guide 6 which would occur when the lamp flashes.
When pictures are taken using the light source apparatus 15 provided with the flash control means 14 shown in FIG. 3, exposure time can be reduced, and less blurred images can be obtained. Furthermore, pictures of the objects located at farther positions can be taken. However, the size of the light source apparatus 15 is large, and this is very inconvenient for users who do not need flashing: they cannot readily move the system and the entire system costs much.
Japanese Patent Laid-Open No. 314980/1988 discloses a light source apparatus which is energized by one of power sources when an element shutter is not employed and is energized by a flashing power source when the element shutter is used. This prior technique has the same configuration as that shown in FIG. 3 and thus suffers from the same problem.